This invention relates to a specialized wheeled vehicle having an endless track often referred to as a caterpiller track.
Ordinary wheeled vehicles presently in use are driven by front-wheel drive, rear-wheel drive or both front and rear-wheel drive systems. These vehicles are capable of travelling at considerable speed on ordinary roads but they tend to slip and skid and thus cannot be driven safely on desert roads, snow or ice-covered roads, muddy roads and other poor road surfaces owing to the fact that they lack special equipment designed for such purposes. Sandy areas are particularly troublesome because once the vehicle begins slipping it is impossible to move either backward or forward. This may chiefly be ascribed to the fact that there is substantially linear contact between the surface of the land and the powered rear wheels of the vehicle so that the wheels begin to burrow into the surface at the outset of slipping and continue until they are deeply entrenched. Should such a situation develop in a desert region and the vehicle becomes completely immobile, the life of the driver could well be imperilled.
In an effort to overcome these disadvantages a number of specialized vehicles have been developed. For example, there is a crawler-type vehicle which is equipped with an endless caterpiller-type track. The crawler, due to a reduced amount of pressure between the tracks and a unit square area of road surface, is capable of travelling over fairly poor roads but it is an expensive vehicle because of its complicated structure. The crawler is also not suited to travelling at high speed and thus cannot traverse long distances. The vehicle consumes an exorbitant amount of fuel. This type of vehicle is used mainly for pulling or pushing purposes and is not intended for large scale transportation of articles. In addition, this type of vehicle is suited for small scale work in a small area but is lacking in workability in large scale work. Furthermore, it is necessary to obtain legal permission before a crawler can utilize on ordinary roads since the tracks are likely to subject the road surfaces to damage.
Another type of specialized vehicle which can be found in the prior art is the so-called semi-crawler which utilizes general purpose tires as front wheels and an endless track in place of rear wheels. However, like the crawler, the semi-crawler can only travel at low speeds and is not suitable for running over long distances. The same problems arise for other types of specialized vehicles as well. For example, vehicles provided with large-size tires having deep, widened treads, or vehicles equipped with a large number of extremely wide tires cannot travel at high speed and are costly because of their complex construction.